Transmission of uplink reference signalling according to different uplink reference signalling configurations

ABSTRACT

A method of operating network infrastructure equipment in a wireless telecommunications network comprising the network infrastructure equipment and a terminal device, wherein the terminal device is operable to transmit uplink reference signalling to support measurements of radio channel conditions between the terminal device and the network infrastructure equipment, wherein the method comprises: receiving, from the terminal device, uplink reference signalling in accordance with a first uplink reference signalling configuration; determining the terminal device should be configured to transmit uplink reference signalling in accordance with a second uplink reference signalling configuration; and transmitting a paging message for the terminal device, wherein the paging message comprises an indication of an identifier for the terminal device and an indication of the second uplink reference signalling configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on PCT filing PCT/EP2017/082858, filedDec. 14, 2017, which claims priority to EP 17151167.8, filed Jan. 12,2017, the entire contents of each are incorporated herein by reference.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus andmethods, and in particular to handling mobility in wirelesstelecommunications systems.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architecture are able to support more sophisticated services than simplevoice and messaging services offered by previous generations of mobiletelecommunication systems. For example, with the improved radiointerface and enhanced data rates provided by LTE systems, a user isable to enjoy high data rate applications such as mobile video streamingand mobile video conferencing that would previously only have beenavailable via a fixed line data connection. The demand to deploy thirdand fourth generation networks is therefore strong and the coverage areaof these networks, i.e. geographic locations where access to thenetworks is possible, is expected to increase rapidly.

However, whilst fourth generation networks can support communications athigh data rate and low latencies from devices such as smart phones andtablet computers, it is expected that future wireless communicationsnetworks, will be expected to efficiently support communications with amuch wider range of devices associated with a wider range of datatraffic profiles, for example including reduced complexity devices,machine type communication devices, high resolution video displays andvirtual reality headsets. Some of these different types of devices maybe deployed in very large numbers, for example low complexity devicesfor supporting the “The Internet of Things”, and may typically beassociated with the transmissions of relatively small amounts of datawith relatively high latency tolerance, whereas other types of device,for example supporting high-definition video streaming, may beassociated with transmissions of relatively large amounts of data withrelatively low latency tolerance.

In view of this there is expected to be a desire for future wirelesscommunications networks, for example those which may be referred to as5G or new radio (NR) system/new radio access technology (RAT) systems,as well as future iterations/releases of existing systems, toefficiently support connectivity for a wide range of devices associatedwith different applications and different characteristic data trafficprofiles, and to operate over a large range of frequencies, for examplefrom hundreds of MHz to 100 GHz. This can be expected to result innetworks with different architectures and operating principles ascompared to currently deployed networks.

Example use cases currently considered to be of interest for nextgeneration wireless communication systems include so-called EnhancedMobile Broadband (eMBB) and Ultra Reliable and Low LatencyCommunications (URLLC). See, for example, the 3GPP document RP-160671,“New SID Proposal: Study on New Radio Access Technology,” NTT DOCOMO,RAN #71 [1].

The introduction of new radio access technology (RAT) systems/networkstherefore gives rise to new challenges for providing efficient operationfor devices operating in new RAT networks, including devices able tooperate in both new RAT networks (e.g. a 3GPP 5G network) and currentlydeployed RAT networks (e.g. a 3GPP 4G network). One particular areawhere new approaches may be helpful is in relation to handovers betweennetwork nodes responsible for communicating with a terminal device,which may be referred to as mobility management. It will be appreciatedin this context terminal device mobility may result from the devicephysically moving relative to the coverage areas of different networknodes or from changing radio conditions associated with differentnetwork nodes for a static device, and the term mobility management maybe used for both scenarios.

With current mobile telecommunications systems, such as those based onthe 3GPP defined UMTS and Long Term Evolution (LTE) based architectures,handover procedures are carried out on the basis of measurements ofdownlink signals broadcast by each of the network nodes. Thesemeasurements are performed by terminal devices and network nodeselection, reselection or handover is then performed on the basis ofthese measurements.

Existing approaches for handling mobility, with the associatedmeasurement report signalling, handover signalling and evaluationprocedures, however, can result in relatively high power consumption bya terminal device and require terminal devices to comprise relativelycomplex equipment for performing such measurements over a range ofdifferent radio frequencies. This results in lower terminal devicebattery life. In addition, existing handover procedures require arelatively large number of messages to exchanged, which results in arelatively high control signalling overhead and increased chance ofhandover failure, particularly in the case of small cells and/or fastmoving terminal devices, because of the time taken to perform themeasurements and signalling.

In view of these drawbacks there is a desire to provide new approachesfor efficiently handling mobility in wireless telecommunicationssystems.

SUMMARY

The present disclosure can help address or mitigate at least some of theissues discussed above.

Respective aspects and features of the present disclosure are defined inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology. The described embodiments,together with further advantages, will be best understood by referenceto the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 schematically represents some aspects of a LTE-type wirelesstelecommunication network which may be configured to operate inaccordance with certain embodiments of the present disclosure;

FIG. 2 schematically represents some aspects of a new radio accesstechnology (RAT) wireless telecommunications network which may beconfigured to operate in accordance with certain embodiments of thepresent disclosure;

FIG. 3 schematically represents some aspects of the new radio accesstechnology (RAT) wireless telecommunications network of FIG. 2; and

FIG. 4 is a signalling ladder diagram schematically representingsignalling/message exchange between elements of the wirelesstelecommunications network of FIG. 3 in accordance with certainembodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating generally in accordance with LTE principles, but which mayalso support other radio access technologies, and which may be adaptedto implement embodiments of the disclosure as described herein. Variouselements of FIG. 1 and certain aspects of their respective modes ofoperation are well-known and defined in the relevant standardsadministered by the 3GPP (RTM) body, and also described in many books onthe subject, for example, Holma H. and Toskala A [2]. It will beappreciated that operational aspects of the telecommunications networksdiscussed herein which are not specifically described (for example inrelation to specific communication protocols and physical channels forcommunicating between different elements) may be implemented inaccordance with any known techniques, for example according to therelevant standards and known proposed modifications and additions to therelevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The core network 102 routes data to and from the terminaldevices 104 via the respective base stations 101 and provides functionssuch as authentication, mobility management, charging and so on.Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, communications device, andso forth. Base stations, which are an example of radio networkinfrastructure equipment/access nodes, may also be referred to astransceiver stations/nodeBs/e-nodeBs, eNB, gNB, and so forth.Furthermore, it will be appreciated the terms base station and cell mayalso sometimes be used interchangeably, for example, the process of aterminal device connecting to the radio access part of a wirelesstelecommunications system might be referred to as accessing a cell oraccessing a base station (or more generally a radio networkinfrastructure equipment). Nonetheless, it will be appreciated in somecases the physical apparatus comprising a base station (radio networkinfrastructure equipment) may comprise equipment for supporting morethan one communication cell and in such cases it may still beappropriate to draw a distinction between base stations and cells.

FIG. 2 is a schematic diagram illustrating a network architecture for anew RAT wireless mobile telecommunications network/system 300 based onpreviously proposed approaches which may also be adapted to providefunctionality in accordance with embodiments of the disclosure describedherein. The new RAT network 300 represented in FIG. 2 comprises a firstcommunication cell 301 and a second communication cell 302. Eachcommunication cell 301, 302, comprises a controlling node (centralisedunit) 321, 322 in communication with a core network component 310 over arespective wired or wireless link 351, 352. The respective controllingnodes 321, 322 are also each in communication with a plurality ofdistributed units (radio network access nodes/remote transmission andreception points (TRPs)) 311, 312 in their respective cells. Again,these communications may be over respective wired or wireless links. Thedistributed units 311, 312 are responsible for providing the radioaccess interface for terminal devices connected to the network. Eachdistributed unit 311, 312 has a coverage area (radio access footprint)341, 342 which together define the coverage of the respectivecommunication cells 301, 302.

In terms of broad top-level functionality, the core network component310 of the new RAT telecommunications system represented in FIG. 2 maybe broadly considered to correspond with the core network 102represented in FIG. 1, and the respective controlling nodes 321, 322 andtheir associated distributed units/TRPs 311, 312 may be broadlyconsidered to provide functionality corresponding to base stations ofFIG. 1. The term radio network infrastructure equipment may be used toencompass these elements and more conventional base station typeelements of wireless telecommunications systems. Thus, radio networkinfrastructure equipment in this context may be generally considered tocomprise at least one transceiver entity (radio network node) fortransmitting and receiving radio signals for communicating with terminaldevices and a controller entity for controlling the operation of thetransceiver entity/entities. For an LTE type architecture of the kindrepresented in FIG. 1, the controller entity and transceiver entity aretypically co-located, i.e. the radio network infrastructure equipmentcomprises a base station 101. However, in an NR type architecture of thekind represented in FIG. 2, the radio network infrastructure equipmentcomprises a controller entity and a plurality of transceiver entities(radio network nodes) which are distributed and not co-located with thecontroller entity, i.e. each radio network infrastructure equipmentcomprises a controlling node 321, 322 and an associated plurality ofremote TRPs/distributed units 311, 312.

A terminal device 400 is represented in FIG. 2 within the coverage areaof the first communication cell 301. This terminal device 400 may thusexchange signalling with the first controlling node 321 in the firstcommunication cell via one of the distributed units 311 associated withthe first communication cell 301. While in some cases communications fora given terminal device may be routed through only one of thedistributed units, it will be appreciated in some other implementationscommunications associated with a given terminal device may be routedthrough more than one distributed unit, for example in a soft handoverscenario and other scenarios. The particular distributed unit(s) throughwhich a terminal device communicates with the associated controllingnode may be referred to as active distributed units for the terminaldevice. The active distributed units for a terminal device may compriseone or more than one distributed unit (TRP/radio network node). Thecontrolling node 321 is responsible for determining which of thedistributed units 311 spanning the first communication cell 301 isresponsible for serving the terminal device 400 when it is connected tothe network (i.e. which of the distributed units are currently activedistributed units for the terminal device). Typically this will be basedon measurements of radio channel conditions between the terminal device400 and respective ones of the distributed units 311. In this regard, itwill be appreciated the subset of the distributed units in a cell whichare currently active for a terminal device will depend, at least inpart, on the location of the terminal device within the cell (since thiscontributes significantly to the radio channel conditions that existbetween the terminal device and respective ones of the distributedunits).

In the example of FIG. 2, two communication cells 301, 302 and oneterminal device 400 are shown for simplicity, but it will of course beappreciated that in practice the system may comprise a larger number ofcommunication cells (each supported by a respective controlling node andplurality of distributed units) serving a larger number of terminaldevices.

It will further be appreciated that FIG. 2 represents merely one exampleof a proposed architecture for a new RAT telecommunications system inwhich approaches in accordance with the principles described herein maybe adopted, and the functionality disclosed herein may also be appliedin respect of wireless telecommunications systems having differentarchitectures. That is to say, the specific wireless telecommunicationsarchitecture for a wireless telecommunications system adapted toimplement functionality in accordance with the principles describedherein is not significant to the principles underlying the describedapproaches.

Certain embodiments of the invention as discussed herein may beimplemented in wireless telecommunication systems/networks according tovarious different architectures, such as the example architectures shownin FIGS. 1 and 2 or in other architectures that may be adopted. It willthus be appreciated the specific wireless telecommunicationsarchitecture in any given implementation is not of primary significanceto the principles described herein. In this regard, certain embodimentsof the disclosure may be described generally in the context of a radionetwork infrastructure equipment (comprising a controller entity and oneor more transceiver entities as discussed above) communicating with aterminal device, wherein the specific nature of the radio networkinfrastructure equipment and the terminal device will depend on thenetwork infrastructure architecture for the implementation at hand. Forexample, in some scenarios the radio network infrastructure equipmentmay comprise an LTE-type base station 101 as shown in FIG. 1 which isadapted to provide functionality in accordance with the principlesdescribed herein, and in other examples the radio network infrastructureequipment may comprise a controlling node 321, 322 and its associatedTRPs 311, 312 of the kind shown in FIG. 2 which are adapted to providefunctionality in accordance with the principles described herein.

As is well understood, various wireless telecommunications networks,such as the LTE-based network represented in FIG. 1 and the NR-basednetwork represented in FIG. 1, support different Radio Resource Control(RRC) modes for terminal devices, typically including: (i) RRC idle mode(RRC_IDLE); and (ii) RRC connected mode (RRC_CONNECTED). When a terminaldevice transmits data, RRC connected mode is generally used. The RRCidle mode, on the other hand, is for terminal devices which areregistered to the network (EMM-REGISTERED), but not currently in activecommunication (ECM-IDLE).

For a terminal device in RRC idle mode the core network is aware thatthe terminal device is present within the network, but the radio accessnetwork (RAN) part (comprising radio network infrastructure equipmentsuch as the base stations 101 of FIG. 1 and the combined TRPs/CUs ofFIG. 2) is not. The core network is aware of the location of idle modeterminal devices at a paging tracking area level but not at the level ofindividual transceiver entities. The core network will generally assumea terminal device is located within the tracking area(s) associated witha transceiver entities most recently used for communicating with theterminal device, unless the terminal device has since provided aspecific tracking area update (TAU) to the network. (As is conventional,idle mode terminal devices are typically required to send a TAU whenthey detect they have entered a different tracking area to allow thecore network to keep track of their location.) Because the core networktracks terminal devices at a tracking area level, it is generally notpossible for the network infrastructure to know which specifictransceiver entities (radio network node) to use when seeking toinitiate contact with a terminal device in idle mode. Consequently, andas is well known, when a core network is required to connect to an idlemode terminal device a paging procedure is used.

In a typical currently deployed network, idle mode terminal devices areconfigured to seek paging messages periodically. For terminal devicesoperating in a discontinuous reception (DRX) mode this occurs each timethey wake up for their DRX active time. Paging signals for a specificterminal device are transmitted in defined frames (PagingFrames)/sub-frames (Paging Occasions) which are derived from theInternational Mobile Subscriber Identifier (IMSI) of the terminaldevice, as well as paging related DRX parameters established in systeminformation transmitted within the network.

In a conventional LTE-based system, a terminal device thus receives andchecks the contents of specific sub-frames (paging occasions) inspecific frames (paging frames) to look for paging signalling. Forexample, in accordance with the standards set out in ETSI TS 136 321V13.0.0 (2016 February)/3GPP TS 36.321 version 13.0.0 Release 13 [3], aPaging Frame (PF) is a downlink radio frame which may contain one ormore Paging Occasion(s) (PO), where a Paging Occasion is a sub-frame inwhich there may be paging signalling. Paging signalling is conveyed on aphysical downlink shared channel (PDSCH) on resources identified from anallocation message addressed to a paging radio network temporaryidentifier (P-RNTI) and conveyed on a physical downlink control channel(PDCCH). P-RNTI is a common identifier for all terminal devices (e.g.set at FFFE in hexa-decimal for the standard defined by ETSI TS 136 321V13.0.0 (2016 February)/3GPP TS 36.321 version 13.0.0 Release 13 [3]).All terminal devices check whether PDCCH at the specific PF/PO includesP-RNTI or not. If there is a PDSCH allocation addressed to P-RNTI in therelevant subframe, the terminal device proceeds to seek to receive anddecode the paging messages transmitted on the allocated resources onPDSCH. The UE then checks the list of IDs contained in the paging recordlist in the received paging message, to determine whether the listcontains an ID corresponding to itself (for example P-TMSI or IMSI), andif so initiates a paging response.

Although the above description has summarised existing LTE pagingprocedures, it is expected that some broadly similar principles may beadopted for future wireless telecommunications networks based on newerradio access technologies (RATs), such as 5G networks.

As already noted above, it is well understood that in wirelesstelecommunications networks, such as an LTE type network, there aredifferent Radio Resource Control (RRC) modes for terminal devices. Forexample, it is common to support an RRC idle mode (RRC_IDLE); and an RRCconnected mode (RRC_CONNECTED).

Generally speaking, in RRC connected mode a terminal device is connectedto radio network infrastructure equipment (e.g. a base station or acontrolling node via a TRP) in the sense of being able to receive userplane data from the radio network infrastructure equipment, and in RRCidle mode the terminal device is not connected to radio networkinfrastructure equipment in the sense of not being able to receive userplane data via from any radio network infrastructure equipment in thenetwork. The RRC connection setup procedure of going from RRC idle modeto RRC connected mode may be referred to as connecting to a cell/radionetwork infrastructure equipment.

One characteristic of the RRC connected mode is the allocation of acell-specific radio network temporary identifier (C-RNTI) to theterminal device to allow the radio network infrastructure equipment towhich the terminal device is radio connected to address communicationsto the terminal device. A terminal device in a conventional RRC idlemode will not be associated with this kind of RNTI.

Another characteristic of the RRC connected mode is the association ofone or more dedicated logical channels with the terminal device to allowthe terminal device to exchange data with the radio networkinfrastructure equipment to which it is connected. A terminal device ina conventional RRC idle mode will not be associated with this kind ofdedicated logical communication channel.

Another characteristic of the RRC connected mode is that a terminaldevice in RRC connected mode will have established a security context byexchanging security settings with the radio network infrastructureequipment to which it is attached as part of its RRC connectionprocedure. A terminal device in a conventional RRC idle mode will not,however, have this kind of established security context.

More generally, radio network infrastructure equipment to which aterminal device is connected in RRC connected mode will retaininformation relating to the terminal device, for example its allocatedC-RNTI, logical channel configuration settings, security settings, andso on, to allow the radio network infrastructure equipment tocommunicate with the terminal device. This information may generally bereferred to as a terminal device context in/at the radio networkinfrastructure equipment.

In accordance with conventional approaches, when a terminal devicereleases its RRC connection with respect to a particular radio networkinfrastructure equipment and transitions to conventional RRC idle mode,the radio network infrastructure equipment releases the terminal devicecontext.

Whilst in RRC idle mode a terminal device will typically still receivesome signalling from radio network infrastructure equipment covering itslocation (i.e. radio network infrastructure equipment within radiosignalling range of its location). For example, in an LTE context anidle mode terminal device will typically receive reference signallingand other broadcast signalling from different radio networkinfrastructure equipment that are in range. Based on this signalling theidle mode terminal device is able to determine what would currently bethe most appropriate radio network infrastructure equipment to connectto if the terminal device were required to establish a connection to thenetwork, for example to transmit uplink data or in response to a pagingrequest. This ongoing procedure/process for determining the mostappropriate radio network infrastructure equipment to connect to isknown as cell selection/reselection. The terminal device willsynchronise to a selected radio network infrastructure equipment anddecode relevant broadcast information, for example informationtransmitted in master information block (MIB) and system informationblock (SIB) transmissions, from the selected radio networkinfrastructure equipment so the terminal device is able to initiate aradio resource connection with the selected radio network infrastructureequipment as and when appropriate. A terminal device will also monitor apaging channel associated with the radio network infrastructureequipment to which it is synchronised in idle mode to identify if anypaging requests are addressed to the terminal device. When a terminaldevice operating in an RRC idle mode wishes to transition to an RRCconnected mode to exchange data with the network, it transmits an RRCconnection request message to the currently selected radio networkinfrastructure equipment to initiate an RRC connection procedure inaccordance with well-established techniques.

Thus to summarise some aspects of RRC idle and connected modes/states,In RRC Connected State, the network is aware of the UE's location at thecell level and has the UE context thereby allowing scheduling ofphysical resources for user data transmissions because the UE (terminaldevice) has been assigned a temporary ID (C-RNTI) which is unique tothat UE within the cell and hence the UE can be directly addressed bythe network. In the Idle Mode, the network is aware of the UE's locationwithin a Tracking Area and does not have the UE context and cannotschedule physical resources for user data transmission because the UEdoes not have a unique identifier within a cell (C-RNTI). The UE movesfrom an Idle Mode to an RRC Connected State by establishing an RRCConnection which assigns a C-RNTI using a random access (RACH)procedure. The UE moves from RRC Connected State to Idle Mode byreleasing its RRC Connection (and hence releasing C-RNTI). In idle mode,a UE is addressed by first paging the cells within the tracking area.The UE monitors for P-RNTI (paging identifier) on PDCCH rather thanC-RNTI as it does in RRC connected state. The paging message which isreceived following P-RNTI detection contains the UE identity, and if theUE receives this it will then respond by establishing an RRC connectionand having a C-RNTI assigned.

The use of RRC idle mode can be beneficial for a terminal device, forexample in terms of power saving. However, a drawback of switching toRRC idle is the signalling overhead associated with establishing a newRRC connection when the terminal device is required to reconnect toradio network infrastructure equipment and exchange data with the radionetwork infrastructure equipment to allow the radio networkinfrastructure equipment to establish a context for the terminal device.This signalling overhead has an impact for the terminal device in termsof using power and also for the wireless telecommunications network as awhole in terms of taking up radio resources that might otherwise be usedfor other communications. Consequently, there is typically a compromiseto be made between entering RRC idle mode frequently (to preserveterminal device power) and remaining in RRC connected mode for longerperiods (to reduce re-connection signalling overhead).

This means that while RRC idle and RRC connected states can helpefficiently support communications in scenarios involving thetransmission of relatively large amounts of data, it has been recognisedthat these states may be less efficient in supporting communications inall scenarios, for example in scenarios in which relatively smallamounts of data are transmitted, potentially relatively frequently, forexample in accordance with some of the new types of traffic profilesthat may be expected to become more prevalent in new telecommunicationsystems.

With this in mind it has been proposed for Release 14 of the 3GPPstandard to consider using a modified approach for RRC modes/states tosupport certain communications. See, for example, the 3GPP document “NewWI proposal: Signalling reduction to enable light connection for LTE”,3GPP TSG RAN Meeting #71, RP-160540, Gothenburg, Sweden, 7-10 Mar. 2016[4].

One proposal is to define a new/modified RRC mode in which the a UE isnot in an active RRC connected mode with the radio access network (RAN),but is considered to be RRC Connected from a CN (core network) point ofview, so that data can be sent without CN-level paging, but with pagingperformed instead at the RAN level, to cause/trigger the UE to resumeRRC connection (enter an RRC connected mode). This modified RRC statemay be referred to as an “RRC connected inactive” state and may havecharacteristics as discussed in the 3GPP document “Text Proposal to TR38.804 on UE states and state transitions for NR”, 3GPP TSG-RAN WG2 #96,R2-168856, 14-18 Nov. 2016 [5]. This approach has the benefit of beingable to allow the UE to enter a more power efficient state, whilereducing the signalling between the CN and the RAN. The overallprocedure allows RAN to take over responsibility for paging the UE,effectively hiding the RRC state transitions and mobility from the CN,and the CN therefore may directly send data as if the UE was stillconnected and in the same cell.

Much like conventional paging procedures at the CN level (e.g. asdiscussed above), paging procedures at the RAN level may be associatedwith a RAN notification area corresponding to the CN tracking areaconcept. That is to say, the radio network transceiver entities (e.g. inbase stations or TRPs) supporting the RAN in a network may be notionallydivided into groups of transceiver entities comprising respective RANnotification areas. A terminal device leaving a RAN notification areamay be configured to inform/update the network of it changing locationin much the same way as a terminal device leaving a conventionaltracking area transmits a tracking area update. In principle the RANnotification areas may correspond with the CN level tracking areas ofthe network in some implementations, and in that sense the terminologynotification area and tracking area may to some extent be usedinterchangeably. However, it will be appreciated there is no need forthe RAN level notification areas/tracking areas to correspond in sizeand arrangement with the CN level tracking areas, and in fact it mayexpected in practice that the RAN level notification areas willtypically be smaller (i.e. comprise fewer radio network nodes) than theCN level paging areas (i.e. what are referred to as tracking areas inLTE terminology), and further more may be terminal device specific.However, the relative sizes of, and the degree of correspondence, ifany, between, the RAN level notification areas and the CN level pagingareas is not significant to the principles described herein.

Thus, from the RAN point of view, an “anchor” network infrastructureequipment (e.g. the last network infrastructure equipment a terminaldevice was connected to) may be defined, which stores the terminalcontext information. When the CN attempts to transmit data to theterminal device, the RAN then attempts to page the terminal device onthe anchor network infrastructure equipment, and if there is noresponse, the paging may then be performed on all of the cells in thetracking area/RAN notification area, in order to locate the terminaldevice. A summary of this approach may be found in the 3GPP document“Evaluation on RAN initiated paging and MME initiated paging”, 3GPPTSG-RAN WG2 Meeting #94, R2-163930, Nanjing, China, 23-27 May, 2016 [6].It will be appreciated there are various aspects of the specific pagingprocedure that may be adopted, for example in terms of whether theanchor radio network infrastructure equipment should instruct othernetwork infrastructure equipment in the RAN tracking/notification areato attempt to page the terminal device at the same time as the anchorradio network infrastructure equipment pages the terminal device or onlyafter failing to successfully page the terminal device, that will dependon the implementation at hand, and are not significant here.

The overall procedure in the RAN part of the network, from a terminaldevice's point of view, may be similar to the suspend/resume procedureintroduced in Release 13 of the 3GPP standards for “Internet of Things”terminal devices. Thus when a terminal device connection to networkinfrastructure equipment is released, a “resume ID” is assigned tocontext information stored in the network for the terminal device, andwhen the terminal device reconnects using the “resume” procedure, theresume ID is used to locate the stored context information for theterminal device in the network.

Recent discussions within the 3GPP community have further consideredissues of notification/tracking in a RRC connected inactive state for 5Gnew Radio (NR or 5G-RAN), for example as set out in the 3GPP documents“RAN based Update mechanism for new RAN state”, 3GPP TSG RAN WG2 Meeting#96, R2-168525, Reno, USA, 14-18 Nov. 2016 [7]; “Discussion on RANnotification area for the new RRC state” 3GPP TSG RAN WG2 Meeting #96,R2-168524, Reno, USA, 14-18 Nov. 2016 [8]; and “Inactive Stateprinciples—RAN based notification area”, 3GPP TSG RAN WG2 Meeting #96,R2-168602, Reno, USA, 14-18 Nov. 2016 [9]. Based on these discussionsvarious aspects relating to using this type of approach have beendiscussed, such as:

-   -   RAN2 should assume that UEs perform CN level location updates        when crossing a TA boundary when in RRC connected inactive mode        (in addition to RAN updates based on RAN notification areas).    -   There will be NG Core/CN Location Area code (similar to Tracking        Area code) broadcast in system information of an NR Cell.    -   RAN based notification area is UE-specific and configurable by        the radio network node via dedicated signalling.    -   There will be a unique global Cell ID broadcast in system        information of NR Cell.    -   For the RRC connected inactive state there will be a way to        configure the UE with a RAN based notification area that is        smaller than a TA.    -   A RAN notification area may cover a single cell or multiple        cells.

In currently deployed telecommunications systems, such as LTE basedsystems, mobility management is typically performed on the basis ofmeasurements by a terminal device of downlink reference signalsbroadcast by network infrastructure equipment (i.e. base stations in anLTE context). However, there have been proposal for future wirelesstelecommunications systems to instead, or additionally, use measurementsby network infrastructure equipment of uplink reference signallingtransmitted by terminal devices to support mobility management. Inparticular, it has been proposed that mobility management for terminaldevices in an RRC connected inactive state should be based onmeasurements of uplink reference signalling, which may be referred to as“uplink based mobility”. See, for example, the 3GPP documents: “ProposedWay Forward on Uplink-Based Mobility”, 3GPP TSG-RAN WG2 Meeting #95bis,R2-167286, Kaohsiung, 10-14 Oct. 2016 [10]; “NR uplink measurement basedmobility in the inactive state” 3GPP TSG-RAN WG2 Meeting #95bis,R2-167066, Kaohsiung, 10-14 Oct. 2016 [11]; “Benefit of UL tracking”3GPP TSG-RAN WG2 Meeting #95bis, R2-166987, Kaohsiung, 10-14 Oct. 2016[12]; and “Energy conserved operation evaluation”, 3GPP TSG-RAN WG2Meeting #95bis, R2-166907, Kaohsiung, 10-14 Oct. 2016 [13]. Thesedocuments may be referred to for more information on the proposals foruplink based mobility.

Thus, for an uplink based mobility approach in an NR architecture of thekind schematically represented in FIG. 2, rather than the terminaldevice 400 performing measurements on downlink signalling transmitted bythe TRPs 311, 312, the terminal device 400 instead transmits uplinkreference signalling which can be measured by the TRPs (distributedunits/transceiver entities) which are in range to receive the uplinkreference signalling. Based on these measurements, the controlling nodefor the communication cell in which the terminal device is located maytrack the location of the terminal device, e.g. to (i) determine whichof the (one or more) distributed units/transceiver entities is mostappropriate for supporting communications between the controlling nodeand the terminal device (i.e. which TRP(s) should be active for theterminal device), and configure their operation accordingly; and/or (ii)determine if the terminal device is approaching the edge of the cellsupported by the controlling node so that a change of cell such as ahandover or reselection procedure should be initiated.

Thus, the radio/channel conditions associated with a communication pathbetween a terminal device and one or more transceiver entities may bedetermined based on measurements of a characteristic of uplink referencesignalling transmitted by the terminal device and received by therespective ones of the transceiver entities. There are a number ofdifferent characteristics of uplink reference signalling that may bemeasured to determine an indication of radio channel conditionsassociated with a radio path between the terminal device and eachrespective radio transceiver entity receiving the reference signalling.For example, the measured characteristic may be an indication of thereceived signal strength or quality of the reference signalling, and acontroller entity (e.g. a controlling node 321, 322 in the examplearchitecture of FIG. 2) may establish a location for the terminal device(in the sense of determining an indication of a position for theterminal device relative to the network of transceiver entities) basedon the measured characteristics. For example, by an interpolationbetween the transceiver entity locations weighted towards thetransceiver entities measuring the greatest power/quality may be used toderive a specific geographic location for the terminal device, or theterminal device location may simply be determined be establishing whichparticular transceiver entity is closest to the terminal device (in thesense of receiving the uplink reference signal with the greatest poweror quality).

Although, as discussed further herein, certain embodiments of thedisclosure are concerned with configuring aspects of uplink basedmobility signalling, it will be appreciate the specific manner in whicha location for the terminal device is derived from the measurements ofuplink signalling, and also the manner in which the derived location isused to manage mobility (e.g. in terms of determining which specifictransceiver entity/entities should be active for the terminal deviceand/or whether a handover procedure should be initiated) will depend onthe implementation at hand and are not significant to the principlesdescribed herein for configuring uplink reference signalling.

FIG. 3 schematically represents some aspects of the wirelesstelecommunications system 300 of FIG. 2 in accordance with certainembodiments of the disclosure. In particular, FIG. 3 shows thecontrolling node 321, eight of the TRPs 311 associated with thecontrolling node 321 (these are identified by reference numerals 311A,311B, . . . 311H in FIG. 3), the core network part 310, and the terminaldevice 400. As previously noted, aspects of the architecture andoperation of the telecommunications system 300 which are notspecifically described herein may be implemented in accordance with anyknown techniques. In line with the terminology discussed above, the TRPs311 and controlling node 321 may be consider together to correspond witha network infrastructure equipment 325 of the system 300 (with othercontrolling nodes and their TRPs, not shown in FIG. 3, providing otherelements of network infrastructure equipment for the system 300).Furthermore, the controlling node 321 may also be referred to as acontroller entity for the network infrastructure equipment 325 and theTRPs 311 may also be referred to as transceiver entities for the networkinfrastructure equipment 325.

Thus, the telecommunications system 310 infrastructure comprises thecore network part 310 and a radio network part comprising the networkinfrastructure equipment 325 made up of the controlling node 321 and theTRPs 311. In FIG. 3 only one controlling node 321 (with eight TRPs 311)and one terminal device 400 are shown for simplicity, but it will ofcourse be appreciated that in practice the radio network part willtypically comprise a larger number of controlling nodes respectivelyassociated with different numbers of TRP and serving a larger number ofterminal devices across various communication cells. The terminal device400 is operable to communicate data to and from the controlling node 321via one or more or the TRPs when in range of the communication cellsupported by the controlling node 321.

The controlling node 321 comprises transceiver circuitry 321 a (whichmay also be referred to as a transceiver/transceiver unit) forcommunicating (wirelessly or otherwise) with the core network 310 andthe TRPs 311 and processor circuitry 321 b (which may also be referredto as a processor/processor unit) configured to control the controllingnode 321 to operate in accordance with embodiments of the presentdisclosure as described herein. The processor circuitry 321 b maycomprise various sub-units for providing functionality in accordancewith embodiments of the present disclosure as explained further herein.These sub-units may be implemented as discrete hardware elements or asappropriately configured functions of the processor circuitry. Thus, theprocessor circuitry 321 b may comprise circuitry which is suitablyconfigured/programmed to provide the desired functionality describedherein using conventional programming/configuration techniques forequipment in wireless telecommunications systems. The transceivercircuitry 321 a and the processor circuitry 321 b are schematicallyshown in FIG. 3 as separate elements for ease of representation.However, it will be appreciated that the functionality of thesecircuitry elements can be provided in various different ways, forexample using one or more suitably programmed programmable computer(s),or one or more suitably configured application-specific integratedcircuit(s)/circuitry/chip(s)/chipset(s). It will be appreciated thecontrolling node 321 will in general comprise various other elementsassociated with its operating functionality.

The respective TRPs/distributed units 311 are functionally identical butserve the different parts of the communication cell 301 supported by thecontrolling node 321, for example as schematically indicated in FIG. 2.Each TRP 311 comprises a transceiver unit (schematically represented asthe upper triangular part each TRP in FIG. 3) for transmission andreception of communications (wirelessly or otherwise) between therespective TRPs 311 and their associated controlling node 321 and alsofor transmission and reception of wireless radio communications betweenthe respective TRPs and terminal devices within their radiocommunication range/footprint. Each TRP 311 further comprises aprocessor unit (schematically represented as the lower rectangular partof each TRP in FIG. 3) configured to control the operation of the TRP311 in accordance with the principles described herein. The respectiveprocessor units of the TRPs may comprise various sub-units. Thesesub-units may be implemented as discrete hardware elements or asappropriately configured functions of the processor unit. Thus, therespective processor units may comprise a processor unit which issuitably configured/programmed to provide the desired functionalitydescribed herein using conventional programming/configuration techniquesfor equipment in wireless telecommunications systems. The respectivetransceiver units and processor units are schematically shown in FIG. 2as separate elements for ease of representation. However, it will beappreciated the functionality of these units can be provided in variousdifferent ways, for example using a single suitably programmed generalpurpose computer, or suitably configured application-specific integratedcircuit(s)/circuitry. It will be appreciated the TRPs will in generalcomprise various other elements, for example a power supply, associatedwith their operating functionality.

The terminal device 400 comprises transceiver circuitry 400 a (which mayalso be referred to as a transceiver/transceiver unit) for transmissionand reception of wireless signals and processor circuitry 400 b (whichmay also be referred to as a processor/processor unit) configured tocontrol the terminal device 400. The processor circuitry 400 b maycomprise various sub-units/sub-circuits for providing functionality inaccordance with embodiments of the present disclosure as describedherein. These sub-units may be implemented as discrete hardware elementsor as appropriately configured functions of the processor circuitry.Thus the processor circuitry 400 b may comprise circuitry which issuitably configured/programmed to provide the desired functionalitydescribed herein using conventional programming/configuration techniquesfor equipment in wireless telecommunications systems. The transceivercircuitry 400 a and the processor circuitry 400 b are schematicallyshown in FIG. 3 as separate elements for ease of representation.However, it will be appreciated that the functionality of thesecircuitry elements can be provided in various different ways, forexample using one or more suitably programmed programmable computer(s),or one or more suitably configured application-specific integratedcircuit(s)/circuitry/chip(s)/chipset(s). It will be appreciated theterminal device 400 will in general comprise various other elementsassociated with its operating functionality, for example a power source,user interface, and so forth, but these are not shown in FIG. 3 in theinterests of simplicity.

The terminal device 400 in the wireless telecommunications systemrepresented in FIG. 3 is configured to transmit uplink reference signalsto facilitate mobility management in accordance with the principles setout above. That is to say, the terminal device is configured to transmituplink reference signalling which is received by ones of the TRPs whichare in range of the terminal device's uplink signalling. The TRPs maymeasure a characteristic of the uplink signalling, for example areceived power, and provide an indication of this to the controllingnode 321. Based on this information, the controlling node 321 maydetermine a location for the terminal device within the communicationcell that supports and control communications with the terminal deviceaccordingly (for example determining which TRPs should be used tocommunicate with the terminal device and whether or not the terminaldevice should be handed over to a neighbouring cell).

In this regard, it may be expected the uplink signalling transmitted bythe terminal device will be configurable, for example to include anindication of an identifier for the terminal device and also to conformto a format the uplink signalling which the local TRPs are configured toreceive, for example in terms of timings and frequency resources used,to allow the TRPs to receive the uplink signalling. Furthermore, it maybe expected that different configurations of uplink signalling may beused in respect of different TRPs. For example, different groups of TRPmay be configured to seek uplink mobility signalling on different radioresources (in terms of time and/or frequency), and different identifiersfor the terminal device may be defined for different groups of TRP (sothat identifies can be reused in different groups of TRP). Furthermore,a terminal device may be configured to transmit uplink referencesignalling at different powers depending on the spatial density of TRPsaround its current location. For example, a terminal device in asparsely populated area may be required to transmit uplink referencesignalling with a higher power than a terminal device in a denselypopulated area.

For the example system 300 schematically represented in FIG. 3, and asschematically indicated by dashed lines in the figure, it is assumed theeight TRPs 311 here are notionally divided into two groups of four TRPs,namely a first group of TRPs 311A-D providing radio coverage in a firstzone 331 and a second group of TRPs 311 E-H providing radio coverage ina second zone 332, and that the terminal device's uplink signalling forthe TRPs in the first zone 331 is different from the terminal device'suplink signalling for the TRPs in the second a zone 332, such that theterminal device uplink signalling requires reconfiguration when movingbetween, or in the vicinity of the boundary of, the two zones 331, 332.Certain embodiments of the disclosure relates to approaches forreconfiguring a terminal device is uplink reference signalling in such ascenario.

FIG. 4 is a ladder diagram schematically showing signalling exchangebetween the controlling node 321, TRPs in the first zone 331, TRPs inthe second zone 332, and the terminal device 400 in accordance withcertain embodiments of the disclosure.

At the beginning of the processing represented in FIG. 3 it is assumedit is assumed the terminal device 400 is located within the geographicfoot print of the first zone 331 in the vicinity of the boundary betweenthe first zone 331 and second zone 331, as schematically shown in FIG.3. It is also assumed the terminal device is not in an active RRCconnected mode but is in an RRC connected inactive mode of the kindrecently proposed and discussed above. It is further assumed that priorto entering the non-active RRC connected mode, the terminal device wasin an active RRC connected mode with respect to the controlling node 321via one or more of the TRPs 311A-D in the first zone 331, for example,because the terminal device was previously involved in an ongoing datacommunication session via one of the these TPRs in the first zone 331.It is further assumed the terminal device is configured to transmituplink reference signalling in accordance with a first configurationcorresponding to that defined for use in the first communication zone331. The configuration settings for the uplink reference signalling forthe terminal device to use in respect of the first zone 331 may havebeen previously configured with the terminal device in the RRC connectedinactive mode in the same way as discussed further below with respect toreconfiguring the terminal device for transmitting uplink referencesignalling for use in the second zone 332, or it may have beenconfigured using conventional signalling exchange whilst in the RRCconnected mode. For example, the terminal device may have beenpreviously configured for transmitting uplink reference signallingappropriate to the first zone 331 when its RRC connection with thecontrolling node 321 via a TRP in the first zone was released.

Thus, in step S1 represented in FIG. 4, the terminal device 400transmits uplink reference signalling in accordance with a firstconfiguration (uplink ref. sig. config. 1). This may be transmitted inaccordance with previously proposed techniques for using uplinkreference signalling in wireless telecommunications systems supportingan RRC connected inactive state, for example as discussed in theabove-referenced documents, such as “NR uplink measurement basedmobility in the inactive state” 3GPP TSG-RAN WG2 Meeting #95bis,R2-167066, Kaohsiung, 10-14 Oct. 2016 [11]. In that regard, the terminaldevice 400 may thus operate in a DRX mode in the RRC connected inactivestate and be configured to transmit uplink reference signalling duringDRX wake-up periods when the terminal device monitors for paging signals(see, for example, FIG. 5 in “NR uplink measurement based mobility inthe inactive state” 3GPP TSG-RAN WG2 Meeting #95bis, R2-167066,Kaohsiung, 10-14 Oct. 2016 [11]).

The configuration for the uplink reference (beacon) signalling mayinclude various settings for different properties of the uplinkreference signalling depending on the implementation at hand. Forexample, parameters/settings that may be configured may include asignature sequence to be used for the uplink reference signalling, anidentifier for the terminal device associated with the uplink referencesignalling (so the network can identify the terminal device sending theuplink reference signalling, a power setting to use for the uplinkreference signalling, a beam direction or being sweep properties to beused for the uplink reference signalling, an indication of physicalradio resources to use for the uplink reference signalling, for examplein terms of time/frequency, an uplink channel configuration for theuplink reference signalling, an indication of a rate of transmission forthe uplink reference signalling. However, it will be appreciated certainembodiments of the disclosure relate to how uplink reference signallingmay be (re)configured/changed, and the specific nature of the uplinkreference signalling in terms of its specific characteristics and thesettings which may be configured are not of primary significance to theprinciples described herein. That is to say, what is of primarysignificance is how the settings can be changed (i.e. how the uplinkreference signalling from a terminal device can be reconfigured) ratherthan what the settings represent in any given implementation.

A number of the TRPs 311 in the first zone 331 will receive and measurea characteristic of the uplink reference signalling, for example areceived power or signal quality, which provides an indication of radiochannel conditions between the terminal device and the respective TRPs(which fundamentally is what may be used to locate the terminal device).The specific characteristic which is measured will depend on theimplementation of uplink based mobility reference signalling at hand. Itmay be expected not all TRPs in the first zone 331 will receive theuplink reference signalling, for example because the uplink signallingis not transmitted with sufficient power to be received by the moredistant TRPs. It will be appreciated TRPs in the second zone 332, inparticular TRPs in the second zone which are close to the boundary ofthe first and second zones near where the terminal device is located,may in principle receive the uplink reference signalling with sufficientpower to decode it, but do not do so because the uplink referencesignalling is transmitted with a configuration which relates to thefirst zone 331, and not the second zone 332.

The TRPs in the first zone (zone 1) 331 which do receive and measure therelevant characteristic of the uplink reference signalling proceed totransmit respective measurement reports to the controlling node 321(along with an indication of the terminal device to which themeasurement report relates), as schematically indicated by step S2 inFIG. 4.

In step S3, the controlling node 321 receives the measurement reportfrom the TRPs that received the uplink reference signalling andestablishes a location for the terminal device within the communicationcell supported by the controlling node 321 based on these measurements.This measurement and evaluation procedure/terminal device locationdetermination may, for example, be performed in accordance withpreviously proposed techniques. More generally, it may be based on anytechniques for establishing a location for a terminal device based onmeasurement of radio conditions between a transceiver entity and theterminal device, regardless of whether the measurements are made inrespect of uplink or downlink beacon signalling.

Having established a location for the terminal device in step S3, thecontrolling node 321 may respond accordingly. For example, thecontrolling node may use this information to determine which transceiverentities 311 should be used to route any communications to/from theterminal device, and may also determine if the terminal device issufficiently close to the boundary of a communication area governed bythe controlling node, that a handover procedure should be initiated.

In this particular example, and as schematically indicated in step S4,the controlling node 321 determines the terminal device is approachingthe boundary between the first zone 331 and the second zone 332.Consequently, the controlling node determines the terminal device shouldbe configured to transmit uplink reference signalling that can bereceived by the transceiver entities 311 E-H in the second zone 332 toallow uplink reference signalling from the terminal device to bereceived by transceiver entities 311 E-H in the second zone to be usedto help determine a location for the terminal device.

In step S5 the controlling node 321 establishes a configuration foruplink reference signalling for the terminal device to use in respect ofthe transceiver entities 311 E-H in the second zone 332, which may bereferred to here as a second uplink reference signalling configuration(uplink ref. sig. config. 2). In this particular example in which thecontrolling node is responsible for the transceiver entities in both thefirst zone and the second zone, the controlling node will have readyaccess to this information because it will have been responsible forconfiguring the transceiver entities accordingly. In other exampleimplementations in which the transceiver entities in the second zone 332are governed by a different controlling node, the controlling nodewishing to establish the uplink configuration settings for the secondzone may, for example, request this information from the othercontrolling node.

In accordance with embodiments of the disclosure, the controlling node321 is configured to provide the terminal device 400 with an indicationof the second uplink reference signalling configuration established instep S5 in association with a paging message for the terminal device.

Thus, as schematically indicated in steps S6 and S7, having establishedthe terminal device 400 should be provided with updated configurationinformation, the controlling node 321 transmits a paging message to theterminal device 400 via one or more of the TRPs in the first zone 331.The paging message of step S6 and S7 includes an identifier for theterminal device that allows the terminal device to determine it is theintended recipient of the paging message. In this regard, the pagingmessage may be transmitted by the network infrastructure equipmentcomprising the controlling node 321 and the TRPs through which themessage is routed to the terminal device generally in accordance withany proposed techniques. However, in accordance with certain embodimentsof the disclosure, the paging message further conveys additionalinformation to the recipient terminal device. In particular, the pagingmessage comprises an indication of the second uplink referencesignalling configuration. This may be provided in various ways. Forexample, the indication of the second configuration may comprise acomplete specification of settings for all parameters relevant fordefining the configuration, specification of settings for only thoseparameters in the second configuration which are different from thecorresponding settings in the first configuration (i.e. a “delta”configuration), or an indication of which one of a plurality ofpredefined (for example configured by system information transmissionsor previous dedicated signalling) configurations correspond with thesecond configuration.

Thus, the paging message of steps S6 and S7 may comprise physicaltransmission resource allocation signalling addressed to a common radionetwork temporary identifier for paging, P-RNTI, with transmissions onthe physical transmission resources indicated by the allocationsignalling containing an identifier for the terminal device and anindication of the new uplink reference signalling configuration for theterminal device to use to allow its uplink reference signalling to bereceived by the transceiver entities in the second zone 332.

In step S8, the terminal device receives the paging message of steps S6and S7 and derives the second uplink reference signalling configurationfrom the indication in the paging message, and configures itself fortransmitting uplink reference signalling in accordance with the seconduplink reference signalling configuration (ref. sig. config. 2).

Accordingly, at this stage of the processing represented in FIG. 4, theterminal device 400 which had previously transmitted uplink referencesignalling in accordance with the first uplink reference signallingconfiguration has been provided with a new/updated configuration for itsuplink reference signalling, as received in association with the pagingmessage transmitted from the controlling node 321 via one or more of theTRPs in the first zone 331.

In the example implementation considered here, it is assumed the networkis configured so that a terminal device at the boundary between twozones is configured to transmit uplink reference signalling inaccordance with both configurations so that transceiver entities in bothzones can receive uplink reference signalling from the terminal device.

Thus, the terminal device transmits uplink reference signalling inaccordance with the first uplink reference signalling configuration, andthis may be received by TRPs in the first zone which are withincommunication range of the terminal device's uplink referencesignalling, as schematically indicated in step S9. This step correspondswith, and will be understood from, step S1 discussed above. In step S10,the TRPs in the first zone which receive the uplink reference signallingtransmitted by the terminal device in accordance with the first uplinkreference signalling configuration forward corresponding measurementreport to the controlling node 321. This step corresponds with, and willbe understood from, step S2 discussed above.

In addition to transmitting uplink reference signalling in accordancewith the first configuration in step S9, the terminal device alsotransmits uplink reference signalling in accordance with the seconduplink reference signalling configuration, and this may be received byTRPs in the second zone which are within communication range of theterminal device's uplink reference signalling, as schematicallyindicated in step S11. This step corresponds with, and will beunderstood from, step S1 discussed above, except for using a differentuplink reference signalling configuration which is relevant fordifferent transceiver entities. In step S12, the TRPs in the second zonewhich receive the uplink reference signalling transmitted by theterminal device in accordance with the second uplink referencesignalling configuration forward corresponding measurement report to thecontrolling node 321. This step corresponds with, and will be understoodfrom, step S3 discussed above, except the signalling is received at thecontrolling node from different transceiver entities.

In step S13, having received measurement reports relating to uplinkreference signalling received by the transceiver entities in both thefirst zone and the second zone, the controlling node 321 evaluates themeasurements to determine a location for the terminal device. This stepis similar to, and will be understood from, step S3 discussed above,although now includes measurement report from TRPs in both zones. Asalready noted, the specific manner in which the measurement reports areevaluated to determine a location for the terminal device, and indeedthe specific action to be taken once the location for the terminaldevice is established, are not of primary significance to the principlesdescribed herein which provide approaches for reconfiguring a terminaldevice to modify an aspect of its uplink reference signalling.

Thus in accordance with the principles described herein, approaches areprovided for reconfiguring uplink reference signalling transmitted by aterminal device to allow measurements of radio channel conditionsbetween the terminal device and respective transceiver entities in awireless telecommunications network/system. Furthermore, thereconfiguration setting for the terminal device may be communicated fromthe network to the terminal device in association with a paging message.Thus the uplink reference signalling for the terminal device may bereconfigured without the terminal device needing to establish an activeradio resource control (RRC) connection with the network, for example,the terminal device may be reconfigured with a new uplink referencesignalling while remaining in an inactive RRC connected mode/state ofthe kind discussed above. What is more, in accordance with certainembodiments of the disclosure, the terminal device may be reconfiguredto transmit uplink reference signalling appropriate for a newzone/region of transceiver entities without needing to acquire systeminformation relating to the new zone of transceiver entities.

In addition to the paging message conveying an indication ofcharacteristics for the terminal device to use for reconfiguring itsuplink reference signalling, in some example implementations the pagingmessage for the terminal device may further comprises an indication of acharacteristic of downlink reference signalling transmitted by one ormore of the transceiver entities in the second zone (e.g. informationidentifying the area or zone identifier transmitted in the downlinkreference signal of the adjacent zone). Accordingly, this can providethe terminal device with information needed for the terminal device toreceive downlink reference signalling from transceiver entities in thesecond zone, again without needing to establish an active RRCconnection. Thus, the updated configuration may instruct the terminaldevice to implement downlink mobility procedures in the adjacentzone/area (or in the overlapping area between the zones). Alternativelythe configuration may instruct the terminal device to implement uplinkmobility procedures in one frequency band and downlink mobilityprocedures in a different frequency band.

In some implementations the uplink reference signalling transmitted bythe terminal device in accordance with the second uplink referencesignalling configuration may be transmitted on a frequency which isoutside a range of frequencies on which the radio transceiver entitiesin the first zone are configured to operate. In this regard, theprocedure for reconfiguring the terminal device may be in relation totriggering transmission of reference signalling for performing aninter-frequency measurement to help determine whether an inter-frequencyreselection should be performed.

As already noted, the terminal device may be configured to transmit theuplink reference signalling in accordance with the second configurationin addition to or instead of transmitting uplink reference signalling inaccordance with the first uplink reference signalling configurationdepending on the situation at hand. For example, if the reconfigurationis to change an aspect of the existing uplink reference signalling, forexample a power setting, the uplink reference signalling in accordancewith the second configuration may replace the uplink referencesignalling in accordance the first configuration. However, if thereconfiguration is to trigger additional uplink reference signalling tobe received by additional transceiver entities, for example as aterminal device is determined to approach a boundary between two zonesof transceiver entities associated with different uplink referencesignalling configurations, uplink signalling in accordance with thesecond configuration may be transmitted in addition to uplink signallingin accordance with the first configuration. Furthermore, as a terminaldevice moves away from a boundary in towards the centre of a zone, thereconfiguration may trigger the terminal device to stop transmittingreference uplink signalling associated with a different zone. That is tosay, a paging-based reconfiguration of a terminal device's uplinkreference signalling may involve reconfiguring a terminal device whichis transmitting uplink reference signalling in accordance with more thanone configuration to stop transmitting uplink reference signalling inaccordance with one or more of the configurations. This provides oneapproach for “switching off” uplink reference signalling transmissionsin accordance with a configuration that is no longer relevant for aterminal device once it moves away from transceiver entities in a zoneassociated with that configuration. Other approaches for deactivatinguplink reference signalling in accordance with a particularconfiguration may involve the use of timers. For example, if a terminaldevice is configured to begin transmitting uplink reference signallingin accordance with a second configuration in addition to transmittinguplink reference signalling in accordance with a first configuration,the terminal device may further be configured to stop transmitting inaccordance with one or other configuration after a given time haselapsed. The paging message which triggered the additional uplinkreference signalling may indicate the timer duration and which of thetwo configurations to stop transmitting (for example based on a futurepredicted/extrapolated location for the terminal device). Alternatively,the duration of a timer may be predefined. In yet another example, aterminal device may be configured to stop transmitting in accordancewith a first configuration after it has undergone a cell change awayfrom the cell associated with the first configuration.

The uplink reference signalling configurations may be associated withdifferent settings for one or more uplink reference signallingcharacteristics. For example, the different configurations may beassociated with different settings for one or more of: (i) an uplinkreference signalling signature sequence for the terminal device to usewhen transmitting the uplink reference signalling; (ii) an identifierfor the terminal device for the terminal device to use when transmittingthe uplink reference signalling; (iii) a transmission power setting forthe terminal device to use when transmitting the uplink referencesignalling; (iv) an indication of a rate at which uplink referencesignalling should be transmitted (e.g. to take account of a changingspeed for a terminal device); an indication of a transmission beamdirection and/or a transmission beam sweep property for the terminaldevice to use when transmitting the uplink reference signalling; (v)radio resources, e.g. in terms of time and/or frequency, for theterminal device to use when transmitting the uplink referencesignalling; (vi) an uplink channel configuration for the terminal deviceto use when transmitting the uplink reference signalling. The uplinkreference signalling transmitted in accordance with the different uplinkreference signalling configurations may, for example, be transmitted ondifferent absolute radio frame channel numbers (ARFCN)/frequencies or atdifferent times on the same absolute radio frequency channel number(ARFCN).

Although the terminal device may be provided with the indication of thechanged configuration information in association with a paging messageto allow the terminal device to receive the reconfiguration informationwithout establishing an active RRC connection or decoding systeminformation messages, in other examples the paging message may instructthe terminal device to obtain configuration information from systeminformation (i.e. the paging message may comprise an indication of asystem information update), for example which contains a configurationfor each of the uplink signals, is available only in the systeminformation which is broadcast on the TRPs around the border betweenzones, if the terminal device has not previously stored theconfiguration. The terminal device may additionally or alternatively beconfigured to receive system information from TRPs belonging to thesecond zone in order that it can start transmitting an uplink signalaccording to the configuration from the second zone. These approachescould be implemented by establishing a new system information block ornew information elements inside an existing system information block.

In the specific example discussed above with reference to FIG. 4, theuplink reference signalling reconfiguration comprises configuring aterminal device which is transmitting uplink reference signalling inaccordance with a first configuration associated with a first group oftransceiver entities to additionally transmit uplink referencesignalling in accordance with a second configuration associated with asecond group of transceiver entities. However, it will be appreciatedthis is merely one example. For example, network infrastructureequipment may be configured to reconfigure a terminal device's uplinkreference signalling in order to modify an aspect of its current uplinkreference signalling, for example to increase power if it is determinedtransceiver entities are not reliably receiving the uplink referencesignalling, or to change an identifier for the terminal device if it isdetermined there is a conflict with an identifier for another terminaldevice that has moved into range of the group of transceiver entitiessupporting the terminal device. That is to say, the process ofreconfiguring a terminal device to modify an aspect of its uplinkreference signalling in accordance with embodiments of the disclosure isnot limited to scenarios in which the reconfiguration is made because ofthe terminal device is approaching a boundary between two groups oftransceiver entities configured to receive uplink reference signallingwith different configurations.

Furthermore, whereas in the example described above with reference toFIGS. 3 and 4 the transceiver entities in the first zone 331 and thetransceiver entities in the second zone 332 are associated with a singlecontrolling node 321 in an NR-type network architecture, as alreadynoted, the same principles can be applied for different networkarchitectures/deployments. For example, in another NR-type networkdeployment, the TRPs in the first zone and the TRPs in the second zonemay be associated with different controlling nodes. In this case thesignalling exchange between the controlling node 321 and the TRPs in thesecond zone represented in FIG. 4 may in effect take place via thecontrolling node for the TRPs in the second zone. Furthermore, it willbe appreciated the same approach can be applied in respect of a moreconventional base-station based network architecture of the kindrepresented in FIG. 1. In this regard, an approach similar to that setout in FIG. 4 may be adopted with the functionality of the left twonodes in FIG. 4 (the controlling node 321 and TRPs in zone 1) beingprovided by one of the base stations 101 in the architecture of FIG. 1,and the functionality of the third-to-left node in FIG. 4 (the TRPs inzone 2) being provided by another of the base stations 101.

For deployments based on different zones of transceiver entities beingassociated with different uplink reference signalling configurations(e.g. as in the example represented in FIGS. 3 and 4), the sizes of therespective uplink zones may in some cases be relatively large (forexample covering entire cities or districts, or covering a train linebetween stations), and so the need to reconfigure a terminal device'suplink reference signalling may in some deployments arise relativelyinfrequently.

Furthermore, for deployments based on different zones of transceiverentities being associated with different uplink reference signallingconfigurations, rather than configure a terminal device to transmitseparate uplink signalling in accordance with different configurationsfor the two zones of transceiver entities, in some approaches a single“common” configuration may be adopted for use in regions betweenneighbouring zones. That is to say, transceiver entities in one zonewhich are in the vicinity of a boundary between two zones may beconfigured to receive uplink reference signalling in accordance withboth a configuration that is specific to their zone (a “zone-wide”configuration) and a configuration which is defined for use at theboundary between zones (a “zone edge” configuration) which transceiverentities in the other zone at the boundary can also receive (i.e.neighbouring zones may have different “zone-wide” configurations but thesame “zone-edge” configuration). Thus, when it is determined a terminaldevice is approaching the boundary between two zones, the terminaldevice may be configured to use the “zone edge” (i.e. “boundary”)configuration which may be received by transceiver entities at theboundary of both zones, rather than transmit separate uplink referencesignalling in accordance with different configurations associated withthe respective zones. When such a terminal device moves away from theboundary, it may be reconfigured to use the relevant “zone-wide”configuration.

Thus there has been described a method of operating networkinfrastructure equipment in a wireless telecommunications networkcomprising the network infrastructure equipment and a terminal device,wherein the terminal device is operable to transmit uplink referencesignalling to support measurements of radio channel conditions betweenthe terminal device and the network infrastructure equipment, whereinthe method comprises: receiving, from the terminal device, uplinkreference signalling in accordance with a first uplink referencesignalling configuration; determining the terminal device should beconfigured to transmit uplink reference signalling in accordance with asecond uplink reference signalling configuration; and transmitting apaging message for the terminal device, wherein the paging messagecomprises an indication of an identifier for the terminal device and anindication of the second uplink reference signalling configuration.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

Paragraph 1. A method of operating network infrastructure equipment in awireless telecommunications network comprising the networkinfrastructure equipment and a terminal device, wherein the terminaldevice is operable to transmit uplink reference signalling to supportmeasurements of radio channel conditions between the terminal device andthe network infrastructure equipment, wherein the method comprises:receiving, from the terminal device, uplink reference signalling inaccordance with a first uplink reference signalling configuration;determining the terminal device should be configured to transmit uplinkreference signalling in accordance with a second uplink referencesignalling configuration; and transmitting a paging message for theterminal device, wherein the paging message comprises an indication ofan identifier for the terminal device and an indication of the seconduplink reference signalling configuration.

Paragraph 2. The method of paragraph 1, wherein the networkinfrastructure equipment comprises a first group of one or more radiotransceiver entities operable to make radio measurements of radiochannel conditions between themselves and the terminal device usinguplink reference signalling transmitted by the terminal device inaccordance with the first uplink reference signalling configuration, andwherein the wireless telecommunications network further comprises asecond group of one or more radio transceiver entities operable to makeradio measurements of radio channel conditions between themselves andthe terminal device using uplink reference signalling transmitted by theterminal device in accordance with the second uplink referencesignalling configuration, and wherein the step of determining theterminal device should be configured to transmit uplink referencesignalling in accordance with a second uplink reference signallingconfiguration comprises determining the terminal device has moved intocommunication range of one or more transceiver entities in the secondgroup.

Paragraph 3. The method of paragraph 2, wherein the paging message forthe terminal device further comprises an indication of a characteristicof downlink reference signalling transmitted by one or more of thetransceiver entities in the second group.

Paragraph 4. The method of paragraph 2 or 3, wherein the uplinkreference signalling transmitted by the terminal device in accordancewith the second uplink reference signalling configuration is transmittedon a frequency which is outside a range of frequencies on which thefirst group of one or more radio transceiver entities are configured tooperate.

Paragraph 5. The method of any preceding paragraph, wherein the pagingmessage comprises an indication the terminal device should transmituplink reference signalling in accordance with the second uplinkreference signalling configuration in addition to uplink referencesignalling in accordance with the first uplink reference signallingconfiguration.

Paragraph 6. The method of any preceding paragraph, wherein the pagingmessage comprises an indication the terminal device should transmituplink reference signalling in accordance with the second uplinkreference signalling configuration instead of uplink referencesignalling in accordance with the first uplink reference signallingconfiguration.

Paragraph 7. The method of any preceding paragraph, wherein the firstuplink reference signalling configuration is associated with a firstsetting for an uplink reference signalling characteristic and the seconduplink reference signalling configuration is associated with a secondsetting for the uplink reference signalling characteristic.

Paragraph 8. The method of paragraph 7, wherein the uplink referencesignalling characteristic comprises an uplink reference signallingsignature sequence for the terminal device to use when transmitting theuplink reference signalling.

Paragraph 9. The method of paragraph 7 or 8, wherein the uplinkreference signalling characteristic comprises an identifier for theterminal device for the terminal device to use when transmitting theuplink reference signalling.

Paragraph 10. The method of any of paragraphs 7 to 9, wherein the uplinkreference signalling characteristic comprises a transmission powersetting for the terminal device to use when transmitting the uplinkreference signalling.

Paragraph 11. The method of any of paragraphs 7 to 10, wherein theuplink reference signalling characteristic comprises an indication of arate at which uplink reference signalling should be transmitted.

Paragraph 12. The method of any of paragraphs 7 to 11, wherein theuplink reference signalling characteristic comprises an indication of atransmission beam direction and/or a transmission beam sweep propertyfor the terminal device to use when transmitting the uplink referencesignalling.

Paragraph 13. The method of any of paragraphs 7 to 12, wherein theuplink reference signalling characteristic comprises radio resources forthe terminal device to use when transmitting the uplink referencesignalling.

Paragraph 14. The method of any of paragraphs 7 to 13, wherein theuplink reference signalling characteristic comprises an uplink channelconfiguration for the terminal device to use when transmitting theuplink reference signalling.

Paragraph 15. The method of any preceding paragraph, wherein theindication of the second uplink reference signalling configurationcomprises an indication of one of plurality of predefined uplinkreference signalling configurations for the terminal device to use forthe second uplink reference signalling configuration.

Paragraph 16. The method of any preceding paragraph, wherein the networkinfrastructure equipment comprises a controller entity and a pluralityor transceiver entities which are remote from the controller entity.

Paragraph 17. The method of any preceding paragraph, wherein the networkinfrastructure equipment comprises a controller entity and a transceiverentity co-located with the controller entity.

Paragraph 18. Network infrastructure equipment for use in a wirelesstelecommunications network comprising the network infrastructureequipment and a terminal device, wherein the terminal device is operableto transmit uplink reference signalling to support measurements of radiochannel conditions between the terminal device and the networkinfrastructure equipment, wherein the radio network infrastructureelement comprises controller circuitry and transceiver circuitryconfigured to operate together such that the radio networkinfrastructure element is operable to: receive, from the terminaldevice, uplink reference signalling in accordance with a first uplinkreference signalling configuration; determine the terminal device shouldbe configured to transmit uplink reference signalling in accordance witha second uplink reference signalling configuration; and transmit apaging message for the terminal device, wherein the paging messagecomprises an indication of an identifier for the terminal device and anindication of the second uplink reference signalling configuration.

Paragraph 19. Circuitry for network infrastructure equipment for use ina wireless telecommunications network comprising the networkinfrastructure equipment and a terminal device, wherein the terminaldevice is operable to transmit uplink reference signalling to supportmeasurements of radio channel conditions between the terminal device andthe network infrastructure equipment, wherein the circuitry comprisescontroller circuitry and transceiver circuitry configured to operatetogether such that the circuitry is operable to: receive, from theterminal device, uplink reference signalling in accordance with a firstuplink reference signalling configuration; determine the terminal deviceshould be configured to transmit uplink reference signalling inaccordance with a second uplink reference signalling configuration; andtransmit a paging message for the terminal device, wherein the pagingmessage comprises an indication of an identifier for the terminal deviceand an indication of the second uplink reference signallingconfiguration.

Paragraph 20. A method of operating a terminal device in a wirelesstelecommunications network comprising the terminal device and networkinfrastructure equipment, wherein the terminal device is operable totransmit uplink reference signalling to support measurements of radiochannel conditions between the terminal device and the networkinfrastructure equipment, wherein the method comprises: transmittinguplink reference signalling in accordance with a first uplink referencesignalling configuration; receiving, from the network infrastructureequipment, a paging message comprising an indication of an identifierfor the terminal device and an indication of a second uplink referencesignalling configuration; and transmitting uplink reference signallingin accordance with the second uplink reference signalling configuration.

Paragraph 21. A terminal device for use in a wireless telecommunicationsnetwork comprising the terminal device and network infrastructureequipment, wherein the terminal device is operable to transmit uplinkreference signalling to support measurements of radio channel conditionsbetween the terminal device and the network infrastructure equipment,wherein the terminal device comprises controller circuitry andtransceiver circuitry configured to operate together such that theterminal device is operable to: transmit uplink reference signalling inaccordance with a first uplink reference signalling configuration;receive, from the network infrastructure equipment, a paging messagecomprising an indication of an identifier for the terminal device and anindication of a second uplink reference signalling configuration; andtransmit uplink reference signalling in accordance with the seconduplink reference signalling configuration.

Paragraph 22. Circuitry for a terminal device for use in a wirelesstelecommunications network comprising the terminal device and networkinfrastructure equipment, wherein the terminal device is operable totransmit uplink reference signalling to support measurements of radiochannel conditions between the terminal device and the networkinfrastructure equipment, wherein the circuitry comprises controllercircuitry and transceiver circuitry configured to operate together suchthat the circuitry is operable to: transmit uplink reference signallingin accordance with a first uplink reference signalling configuration;receive, from the network infrastructure equipment, a paging messagecomprising an indication of an identifier for the terminal device and anindication of a second uplink reference signalling configuration; andtransmit uplink reference signalling in accordance with the seconduplink reference signalling configuration.

REFERENCES

-   [1] 3GPP document RP-160671, “New SID Proposal: Study on New Radio    Access Technology,” NTT DOCOMO, RAN #71, Gothenburg, Sweden, 7    to 10. March, 2016-   [2] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John Wiley and Sons, 2009-   [3] ETSI TS 136 321 V13.0.0 (2016 February)/3GPP TS 36.321 version    13.0.0 Release 13-   [4] “New WI proposal: Signalling reduction to enable light    connection for LTE”, 3GPP TSG RAN Meeting #71, RP-160540,    Gothenburg, Sweden, 7-10 Mar. 2016-   [5] “Text Proposal to TR 38.804 on UE states and state transitions    for NR”, 3GPP TSG-RAN WG2 #96, R2-168856, 14-18 Nov. 2016-   [6] “Evaluation on RAN initiated paging and MME initiated paging”,    3GPP TSG-RAN WG2 Meeting #94, R2-163930, Nanjing, China, 23-27 May,    2016-   [7] “RAN based Update mechanism for new RAN state”, 3GPP TSG RAN WG2    Meeting #96, R2-168525, Reno, USA, 14-18 Nov. 2016-   [8] “Discussion on RAN notification area for the new RRC state” 3GPP    TSG RAN WG2 Meeting #96, R2-168524, Reno, USA, 14-18 Nov. 2016-   [9] “Inactive State principles—RAN based notification area”, 3GPP    TSG RAN WG2 Meeting #96, R2-168602, Reno, USA, 14-18 Nov. 2016-   [10] “Proposed Way Forward on Uplink-Based Mobility”, 3GPP TSG-RAN    WG2 Meeting #95bis, R2-167286, Kaohsiung, 10-14 Oct. 2016-   [11] “NR uplink measurement based mobility in the inactive state”    3GPP TSG-RAN WG2 Meeting #95bis, R2-167066, Kaohsiung, 10-14 Oct.    2016-   [12] “Benefit of UL tracking” 3GPP TSG-RAN WG2 Meeting #95bis,    R2-166987, Kaohsiung, 10-14 Oct. 2016-   [13] “Energy conserved operation evaluation”, 3GPP TSG-RAN WG2    Meeting #95bis, R2-166907, Kaohsiung, 10-14 Oct. 2016

What is claimed is:
 1. A method of operating network infrastructureequipment in a wireless telecommunications network comprising thenetwork infrastructure equipment and a terminal device, wherein theterminal device is operable to transmit uplink reference signalling tosupport measurements of radio channel conditions between the terminaldevice and the network infrastructure equipment, wherein the methodcomprises: receiving, from the terminal device, uplink referencesignalling in accordance with a first uplink reference signallingconfiguration; determining the terminal device should be configured totransmit uplink reference signalling in accordance with a second uplinkreference signalling configuration; and transmitting a paging messagefor the terminal device, wherein the paging message is transmitted in adedicated paging frame and comprises an indication of an identifier forthe terminal device and an indication of the second uplink referencesignalling configuration.
 2. The method of claim 1, wherein the pagingmessage comprises an indication the terminal device should transmituplink reference signalling in accordance with the second uplinkreference signalling configuration in addition to uplink referencesignalling in accordance with the first uplink reference signallingconfiguration.
 3. The method of claim 1, wherein the paging messagecomprises an indication the terminal device should transmit uplinkreference signalling in accordance with the second uplink referencesignalling configuration instead of uplink reference signalling inaccordance with the first uplink reference signalling configuration. 4.The method of claim 1, wherein the first uplink reference signallingconfiguration is associated with a first setting for an uplink referencesignalling characteristic and the second uplink reference signallingconfiguration is associated with a second setting for the uplinkreference signalling characteristic.
 5. The method of claim 4, whereinthe uplink reference signalling characteristic comprises an uplinkreference signalling signature sequence for the terminal device to usewhen transmitting the uplink reference signalling.
 6. The method ofclaim 4, wherein the uplink reference signalling characteristiccomprises an identifier for the terminal device for the terminal deviceto use when transmitting the uplink reference signalling.
 7. The methodof claim 4, wherein the uplink reference signalling characteristiccomprises a transmission power setting for the terminal device to usewhen transmitting the uplink reference signalling.
 8. The method ofclaim 4, wherein the uplink reference signalling characteristiccomprises an indication of a rate at which uplink reference signallingshould be transmitted.
 9. The method of claim 4, wherein the uplinkreference signalling characteristic comprises an indication of atransmission beam direction and/or a transmission beam sweep propertyfor the terminal device to use when transmitting the uplink referencesignalling.
 10. The method of claim 4, wherein the uplink referencesignalling characteristic comprises radio resources for the terminaldevice to use when transmitting the uplink reference signalling.
 11. Themethod of claim 4, wherein the uplink reference signallingcharacteristic comprises an uplink channel configuration for theterminal device to use when transmitting the uplink referencesignalling.
 12. The method of claim 1, wherein the indication of thesecond uplink reference signalling configuration comprises an indicationof one of plurality of predefined uplink reference signallingconfigurations for the terminal device to use for the second uplinkreference signalling configuration.
 13. The method of claim 1, whereinthe network infrastructure equipment comprises a controller entity and aplurality or transceiver entities which are remote from the controllerentity.
 14. The method of claim 1, wherein the network infrastructureequipment comprises a controller entity and a transceiver entityco-located with the controller entity.
 15. A method of operating networkinfrastructure equipment in a wireless telecommunications networkcomprising the network infrastructure equipment and a terminal device,wherein the terminal device is operable to transmit uplink referencesignalling to support measurements of radio channel conditions betweenthe terminal device and the network infrastructure equipment, whereinthe method comprises: receiving, from the terminal device, uplinkreference signalling in accordance with a first uplink referencesignalling configuration; determining the terminal device should beconfigured to transmit uplink reference signalling in accordance with asecond uplink reference signalling configuration; and transmitting apaging message for the terminal device, wherein the paging messagecomprises an indication of an identifier for the terminal device and anindication of the second uplink reference signalling configuration,wherein the network infrastructure equipment comprises a first group ofone or more radio transceiver entities operable to make radiomeasurements of radio channel conditions between themselves and theterminal device using uplink reference signalling transmitted by theterminal device in accordance with the first uplink reference signallingconfiguration, and wherein the wireless telecommunications networkfurther comprises a second group of one or more radio transceiverentities operable to make radio measurements of radio channel conditionsbetween themselves and the terminal device using uplink referencesignalling transmitted by the terminal device in accordance with thesecond uplink reference signalling configuration, and wherein the stepof determining the terminal device should be configured to transmituplink reference signalling in accordance with a second uplink referencesignalling configuration comprises determining the terminal device hasmoved into communication range of one or more transceiver entities inthe second group.
 16. The method of claim 15, wherein the paging messagefor the terminal device further comprises an indication of acharacteristic of downlink reference signalling transmitted by one ormore of the transceiver entities in the second group.
 17. The method ofclaim 15, wherein the uplink reference signalling transmitted by theterminal device in accordance with the second uplink referencesignalling configuration is transmitted on a frequency which is outsidea range of frequencies on which the first group of one or more radiotransceiver entities are configured to operate.
 18. Networkinfrastructure equipment for use in a wireless telecommunicationsnetwork comprising the network infrastructure equipment and a terminaldevice, wherein the terminal device is operable to transmit uplinkreference signalling to support measurements of radio channel conditionsbetween the terminal device and the network infrastructure equipment,wherein the radio network infrastructure element comprises controllercircuitry and transceiver circuitry configured to operate together suchthat the radio network infrastructure element is operable to: receive,from the terminal device, uplink reference signalling in accordance witha first uplink reference signalling configuration; determine theterminal device should be configured to transmit uplink referencesignalling in accordance with a second uplink reference signallingconfiguration; and transmit a paging message for the terminal device,wherein the paging message is transmitted in a dedicated paging frameand comprises an indication of an identifier for the terminal device andan indication of the second uplink reference signalling configuration.19. A terminal device for use in a wireless telecommunications networkcomprising the terminal device and network infrastructure equipment,wherein the terminal device is operable to transmit uplink referencesignalling to support measurements of radio channel conditions betweenthe terminal device and the network infrastructure equipment, whereinthe terminal device comprises controller circuitry and transceivercircuitry configured to operate together such that the terminal deviceis operable to: transmit uplink reference signalling in accordance witha first uplink reference signalling configuration; receive, from thenetwork infrastructure equipment in a dedicated paging frame, a pagingmessage comprising an indication of an identifier for the terminaldevice and an indication of a second uplink reference signallingconfiguration; and transmit uplink reference signalling in accordancewith the second uplink reference signalling configuration.